Regarding antitumor substances, a lot of compounds have heretofore been put to practical use as medicines. However, these are not always satisfactory in view of the pharmaceutical effect and/or the harmful aftereffect thereof. Accordingly, diversified studies have been made in order to develop more excellent antitumor substances.
For instance, Bishop, J. H. reported that a certain kind of genetic products have a tyrosine-specific protein-kinase property (A. Rev. Biochem., 52, 301-354 (1983)). In addition, Cohen, S. et al. reported that a tyrosine-specific protein-kinase participates in the process of the propagation of cells by a variety of cell growth factors as a signal substance (J. Biol. Chem., 257, 1523-1531 (1982)) On the other hand, the present inventors screened, paying their attention to the said phenomena, inhibitors against tyrosine-specific protein-kinase activity widely from the natural world and found that a substance of the formula: ##STR2## as produced by microorganisms belonging to the genus Streptomyces can inhibit the said protein-kinase activity in a low concentration and further has antimicrobial activity and antitumor activity. This was designated MH435-A and was already proposed (Refer to Japanese patent application No. 147039/85).
In addition, the present inventors formed a variety of MH435-A substance analogues by chemical synthesis in order to obtain compounds having a higher physiological activity and have found that some benzene compounds which are substituted by an isonitrilevinyl group, formamidovinyl group, formamidethylene group, lower alkanoylaminovinyl group or lower alkanoylaminoethylene group on the benzene ring and which are further nuclear-substituted by optionally protected hydroxyl group(s) or a halogen atom are in no way inferior to the above-mentioned MH435-A substance in the physiological activity and thus have achieved the present invention.